Flow at the SPS and RHIC as a Quark Gluon Plasma Signature

TL;DR

With the EOS fixed from SPS data, predictions at RHIC are quantified where the quark-gluon plasma (QGP) pressure is expected to drive additional radial and elliptic flows and the strong elliptic flow observed in the first RHIC measurements does not conclusively signal this nascent QGP pressure.

Abstract

Radial and elliptic flow in non-central heavy ion collisions can constrain the effective Equation of State(EoS) of the excited nuclear matter. To this end, a model combining relativistic hydrodynamics and a hadronic transport code(RQMD [17]) is developed. For an EoS with a first order phase transition, the model reproduces both the radial and elliptic flow data at the SPS. With the EoS fixed from SPS data, we quantify predictions at RHIC where the Quark Gluon Plasma(QGP) pressure is expected to drive additional radial and elliptic flow. Currently, the strong elliptic flow observed in the first RHIC measurements does not conclusively signal this nascent QGP pressure. Additional measurements are suggested to pin down the EoS.

Figures (5)

• Figure 1: The pressure versus the energy density($\epsilon$) for different EoSs (see text). EoSs with Latent Heats $0.4\,GeV/fm^{3}$, $0.8\,GeV/fm^{3}$,... are labeled as LH4, LH8,...etc.
• Figure 2: The transverse mass slope($T_{slope}$) as a function of the total charged particle multiplicity in PbPb collisions at an impact parameter of b=6 fm (see also Kataja-MixedPhaseHydroUrqmd). For consistency with the elliptic study in Fig. \ref{['psPionV2dNdy']}, we show b=6 fm although the NA49 data pointsNA49-Slopes are for the 5% most central events, or b$<$3.5 fm. For all EoSs at the SPS, the proton slope parameters at b=6 fm are $\approx7\,MeV$ smaller than at b=0 fm, as for the b=0 LH8 curve. The difference is negligible for $\pi^{-}$.
• Figure 3: (a) The number elliptic flow parameter $v_2$ as a function of the charged particle multiplicity in PbPb collisions at a an impact parameter of b=6 fm. At the SPS, the NA49 $v_2$ data point is extrapolated to b=6 fm using Fig. 3 in NA49-BDependence. At RHIC, the STAR $v_2$ data point is extrapolated to $N_{ch}/N_{ch}^{max}=0.545$ (b=6 fm in AuAu) using Fig. 3 in STAR-Elliptic. The comparison to data is a little unfair: For the model, $v_{2}$ is calculated using all pions in PbPb collisions. For the NA49 data, $v_{2}$ is measured using only $\pi^{-}$ in PbPb (a -3% correction to the model). For the STAR data, $v_{2}$ is measured using charged hadrons in AuAu (a +5% correction to the model).
• Figure 4: $v_2$ versus the number of participants($N_{p}$) relative to the maximum . The model and the NA49 $v_{2}$ valuesNA49-BDependence at the SPS are for $\pi^{-}$. The NA49 data are mapped from b to participants usingNA49-Glauber. The model and the STAR $v_{2}$ valuesSTAR-Elliptic at RHIC are for charged particles. The model does not include weak decays. The number of charged particles is assumed proportional to $N_{p}$.
• Figure 5: Elliptic flow of charged pions as a function of $P_{T}$ and centrality for AuAu collisions at RHIC. For centrality selections The percentages shown 0-11%, 11-45% and 45-85%, indicate the fraction of the total geometric cross section for three centrality selections 0 fm$<$b$<$4.2 fm, 4.2 fm$<$b$<$8.4 fm and 8.4 fm$<$b$<$11.6 fm. The preliminary data points were presented inQM2001Snellings-QM2001. The model curves were found by parameterizing the model data points and averaging over the specified impact range with the geometric weight, $2\pi b\,db$.